Leopard is setting RWIN too large!!!

I was able to accomplish these changes:

sudo sysctl -w net.inet.tcp.sendspace=64240
sudo sysctl -w net.inet.tcp.recvspace=64240

and the TCP analyzer reads not much differently to my untrained eyes:

« SpeedGuide.net TCP Analyzer Results »
Tested on: 10.29.2007 16:37
IP address: 70.181.xxx.xxx

TCP options string: 020405b4010303000101080a2b9d12a20000000004020000
MSS: 1460
MTU: 1500
TCP Window: 65160 (NOT multiple of MSS)
RWIN Scaling: 0
Unscaled RWIN : 65160
Reccomended RWINs: 64240, 128480, 256960, 513920
BDP limit (200ms): 2606kbps (326KBytes/s)
BDP limit (500ms): 1043kbps (130KBytes/s)
MTU Discovery: ON
TTL: 50
Timestamps: ON
SACKs: ON
IP ToS: 00000000 (0)

When trying to access </etc/sysctl.conf> to make the change permanent in Terminal, I get this response:

/etc/sysctl.conf
-bash: /etc/sysctl.conf: Permission denied

Whattaya think?

Correction: I see now that the Unscaled RWIN has doubled to 65160, as desired. I guess I just need help now making the alteration permanent. Thanks in advance, Scott! You've been tremendously helpful.

By the way, under the new settings, testmy.net indicates a screaming improvement in my internet download speed:

Your connection is: 8386 Kbps or 8.4 Mbps
You downloaded at: 1024 kB/s

Thanks again...

You can use the procedure in my previous post:

open the terminal
cd /etc
sudo pico sysctl.conf

<make your changes>

ctrl x (enter "Y" to "yes" to save the pic)
return when prompted for the filename: sysctl.conf

you should be out of the file

You need superuser privs to edit files in /etc

try using sudo

Fantastic, now I can use VPN from home and connect to all my windows shares.

Thanks

Scott,

Scott Micciche wrote:
I've been a Unix sysadmin for 19 years, editing files isn't as scary as some think. 🙂

Easy for you to say!!!!

Thank you so much for that fix. Although I am new to the Mac, I have been around computers for a long time, an old DOS junkie. Unix is completely new to me, but the process seems similar. I just don't know all the commands yet.

I followed your excellent post and my internet speed is right back where it was before the Leopard install. RWIN at 66608 with DSL connection. I am going to check our iMac next.


Thanks again

null

Scott: I was able to modify the file in sudo as per your direction. Here's what speedguide.net reports now:

« SpeedGuide.net TCP Analyzer Results »
Tested on: 10.29.2007 17:34
IP address: 70.181.xxx.xxx

TCP options string: 020405b4010303030101080a078e3a690000000004020000
MSS: 1460
MTU: 1500
TCP Window: 524280 (NOT multiple of MSS)
RWIN Scaling: 3
Unscaled RWIN : 65535
Reccomended RWINs: 64240, 128480, 256960, 513920
BDP limit (200ms): 20971kbps (2621KBytes/s)
BDP limit (500ms): 8388kbps (1049KBytes/s)
MTU Discovery: ON
TTL: 50
Timestamps: ON
SACKs: ON
IP ToS: 00000000 (0)

Is this the expected result? Thanks...

Looks quite right, I usually use the dslreports.com tweak test, but it accomplishes the same thing you have here.

Well, it certainly feels right; my connection is even faster now:

Your connection is: 12481 Kbps or 12.5 Mbps
You downloaded at: 1524 kB/s

You rock!

Glad that worked out, I guess the purported "network auto-tuning" in Leopard isn't always the most efficient for some networks.

Hi All,
Testing all the fixes now. You can use TextWrangler to edit a sysctl.conf file. Make sure you set the text option to "Unix."
Rod

Any ideas on how to change the MTU? It won't stay at 1500.

I do the sudo ifconfig en1 mtu 1500

but obviously, that doesn't keep after reload.

thx!

on tiger:

kern.exec: unknown type returned
net.inet.tcp.sockthreshold: 256
charlie-schloss-computer:~ charlieschloss$

Are you using a PPoE connection by any chance? I believe there is a place in the advanced networking to specify your MTU.